It is well known in the art to utilize rotary headers on self-propelled and/or pull-type machines. Such headers typically have a pair of upright end panels at opposite ends of the cutter bar that project forwardly from the cutter bar and define a crop-receiving space immediately ahead of the cutter bar and between the end panels. Horizontal top panel structure overlies and covers the crop-receiving space so that the space is enclosed across the top and down the sides but is open at the front to define a mouth where the standing crop materials enter the header. The transverse front edge of the horizontal top panel structure serves as a lean bar to deflect the top ends of standing crop materials forwardly with respect to the direction of travel of the header so that the lower ends of the crop materials enter the mouth first for cutoff. Consequently, the severed crop materials are encouraged to enter conditioning mechanism behind the cutter bar butt-end-first for orderly processing and handling. Protective rubberized curtains typically hang from the lean bar across the mouth of the receiving space.
Tall, stalky crops such as forage sorghum can be particularly difficult to harvest and condition with rotary headers because the stalks of one row frequently become tangled and interlocked with stalks in an adjacent row. Consequently, at opposite ends of the header where the end panels are supposed to separate stalks of a row being harvested from those in an adjacent row outside the header, the tangled, crisscrossed stalks simply cannot be separated by the end panels and acted upon by the lean bar in a manner to properly direct the stalks into the restricted confines of the mouth of the header.